JPH11326004A - Coriolis mass flow instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance insulating property of an inside vibration and to increase stability, accuracy and anti-vibration property by providing a vibration tube having one gentle curved portion symmetrical to a center line positioned at an equal distance from an upstream side fixed end and a downstream side fixed end and singly vibrating on a circumferential line at respective predetermined distance from respective points of a reference axis making a straight line connecting the upstream side fixed end and the downstream side fixed end as the reference axis. SOLUTION: A vibration tube 11 is symmetrical to a center line 14 positioned at an equal distance from an upstream side fixed end 12 and a downstream side fixed end 13 and has one gently curved portion 15 and comprised one vibration tube carrying out a simple harmonic motion on a circumferential line at respective predetermined distance from respective points of a reference axis 16 making a straight line connecting the upstream side fixed end 12 and the downstream side fixed end 13 as the reference axis 16. The vibration tube 11 has a shape approximately satisfying an expression: h<0.2L when a distance between the fixed end 12 and the fixed end 13 is defined as L and a distance between the base axis 16 and the tube 11 is defined as h. An exciter 17 is provided on a center portion of the tube 11 and vibration detecting sensors 18, 19 are provided on both sides of the tube 11. The tube 11 only vibrates on a circumferential surface positioned at an equal distance from the reference axis 16, a length of the tube 11 is not varied and axial tensile force is always kept at a constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Coriolis mass flowmeter having improved stability, accuracy and vibration resistance by improving the insulation of internal vibration.

[0002]

2. Description of the Related Art FIG. 46 is an explanatory view of the structure of a conventional example generally used in the prior art.
No. 12 shows a conventional example. In the figure, both ends of a vibration tube 1 are attached to a flange 2. Vibrating tube. The flange 2 is for attaching the vibration tube 1 to the conduit A.

[0003] The exciter 3 is provided at the center of the vibration tube 1. The vibration detection sensors 4 and 5 are the vibration tube 1
Are provided on both sides. In the housing 6, both ends of the vibration tube 1 are fixed.

In the above configuration, the measurement fluid is flowed through the vibration tube 1 and the exciter 3 is driven. Assuming that the angular velocity “ω” in the vibration direction of the exciter 3 and the flow velocity “V” of the measurement fluid (hereinafter, a symbol surrounded by “” represents a vector amount),

The mass flow rate can be measured by measuring the amplitude of the vibration proportional to the Coriolis force in which the Coriolis force of Fc = −2 m “ω” × “V” acts.

FIG. 47 is an explanatory view of the configuration of another conventional example generally used. In this conventional example, the vibration tube 1 is a two-tube type.

[0007]

In a general single-tube Coriolis mass flow meter as shown in FIG. 46, a vibration tube 1 is used.
Is fixed at both ends, but the end point cannot be completely fixed with a flowmeter of a limited size, and the end point slightly vibrates.

The following causes can be considered as the reason why the vibration occurs. When the vibration tube 1 in which the fluid flows is deformed (approximately in a first-order mode resonance state) as shown in FIG. 48, the length of the tube becomes longer due to the deformation, so that a tensile stress is generated in the axial direction of the vibration tube. I do.

For example, φ9.6 × 0.91 of stainless steel
When the center portion of the 400 L vibrating tube 1 is deformed by 1 mm, a tensile force of 7.5 kgf is generated in the axial direction as shown in FIG.

When the vibrating tube 1 is excited in the primary resonance mode, the tensile force is maximized when the plus and minus deformations are maximum, and the tensile force is minimum and zero when the basic shape has no deformation. .

In one cycle of the excitation vibration, the tensile force repeats maximum and minimum twice. That is, the axial pulling force of the vibration tube 1 is generated at twice the frequency of the excitation frequency. The following problems occur when there is vibration due to this pulling force.

If the vibration isolation is insufficient, (1) the Q value becomes low, so that the internal vibration becomes unstable, and it becomes susceptible to extra vibration noise other than the excitation vibration. (2) Large energy is required for excitation, and power consumption increases.

(3) The degree of vibration leakage greatly changes, the vibration state of the vibrating tube also changes, and the zero point and span tend to change due to the installation method, environmental changes such as pipe stress and temperature, and external factors. In other words, Coriolis flowmeters that are unstable with respect to these environmental changes and external factors and have poor vibration resistance and accuracy tend to be poor.

On the other hand, in the conventional example shown in FIG. 47, the two vibrating tubes 1 vibrate in opposite directions, so that the forces cancel each other out at the branch portion, and as shown in FIGS. It has a structure that is hard to leak outside. However, the structure of one vibration tube without a branch point cannot be obtained.

The present invention solves this problem. An object of the present invention is to provide a Coriolis mass flowmeter in which stability, accuracy and vibration resistance are improved by improving insulation of internal vibration.

[0016]

In order to achieve the above object, the present invention provides: (1) a measuring fluid flowing in a vibrating tube, and a flow of the measuring fluid and a Coriolis force generated by angular vibration of the vibrating tube; A Coriolis mass flowmeter that deforms and vibrates the vibrating tube, wherein the upstream fixed end is at least one gently curved portion that is line-symmetric with respect to a midline equidistant from the upstream fixed end and the downstream fixed end. A Coriolis mass flow rate comprising a single vibrating tube that makes a simple vibration on a circumferential line having a predetermined distance from each point of the reference axis, with a straight line connecting the end and the downstream fixed end as a reference axis. Total. (2) a plate-shaped vibrator that is orthogonal to the reference axis or the vibrating tube, one end of which is fixed to the vibrating tube, and the other end of which is disposed on a side opposite to the vibrating tube with respect to the reference axis; 2. The Coriolis according to claim 1, wherein the mass distribution and shape of the vibrating tube and the mass distribution and shape of the vibrating body are adjusted so that the center of gravity of the entire vibration system is arranged on the reference axis. Mass flow meter. (3) at least one end is orthogonal to the reference axis or the vibrating tube, one end of which is fixed to the vibrating tube and the other end is disposed on the opposite side of the vibrating tube with respect to the reference axis and is symmetrical with respect to the center line; The vibrating tube is provided with a plurality of plate-shaped vibrators, and the mass distribution, shape, and rigidity of the vibrating tube, and the mass distribution, shape, rigidity, and interval of the vibrating tube are adjusted so that the center of gravity of the entire vibration system is excited vibration. 3. The Coriolis mass flowmeter according to claim 1, wherein the Coriolis mass flowmeter is arranged at a position of a vibration node. (4) At least two ends perpendicular to the reference axis or the vibrating tube are fixed at one end to the vibrating tube and the other end is arranged on the opposite side of the vibrating tube with respect to the reference axis and symmetrical to the center line. Comprising a plurality of plate-shaped vibrators, the mass distribution and shape and rigidity of the vibrating tube, and adjusting the mass distribution, shape, rigidity and spacing of the vibrating tube to adjust the vibration distribution of the vibrating tube in a steady excitation state. 4. The apparatus according to claim 1, wherein a force generated at both ends fixed portions is only a torsional component around the reference axis so that a component orthogonal to the reference axis due to an exciting force by the exciter is not generated. A Coriolis mass flowmeter according to claim 3. (5) a plate-shaped vibrating body orthogonal to the reference axis or the vibrating tube, one end of which is fixed to the vibrating tube, and the other end of which is disposed on the opposite side of the vibrating tube with respect to the reference axis; 5. The Coriolis mass flowmeter according to claim 1, further comprising a vibration detection sensor provided at the other end of the mass flowmeter. (6) The Coriolis mass flowmeter according to any one of claims 1 to 5, further comprising: an exciter configured to excite the vibrating tube in a higher-order vibration mode than a second-order vibration mode. (7) A compensator provided in parallel with the reference axis and having both ends fixedly supported at both ends of the vibrating tube, a compensator fixedly supported at both ends of the vibrating tube, and the compensator and the vibrating tube The Coriolis mass flowmeter according to any one of claims 1 to 6, further comprising an exciter and a detector provided between the mass flowmeter and the detector. (8) A flexible structure portion provided on the vibration tube between the upstream fixed end, the downstream fixed end, and the compensator for absorbing expansion and contraction in the direction of the reference axis and rotational vibration around the reference axis. The Coriolis mass flowmeter according to claim 7, wherein the mass flowmeter is provided. It is what constituted.

[0017]

In the above construction, when the measuring fluid is flowed through the vibrating tube and the exciter is driven, Coriolis force acts.
By measuring the amplitude of the vibration proportional to the Coriolis force, the mass flow rate can be measured.

The vibrating tube uses a straight line connecting the upstream fixed end and the downstream fixed end as a reference axis, and performs a simple vibration or a circular motion on a circumferential line at a predetermined distance from each point of the reference axis. By doing so, vibration isolation from the outside is enhanced. Hereinafter, a detailed description will be given based on embodiments.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory view of a main part of an embodiment of the present invention, and FIG. 2 is a side view of FIG. In the figure,
46 have the same functions as in FIG. Hereinafter, only differences from FIG. 46 will be described.

The vibrating tube 11 is symmetrical about a middle line 14 equidistant from the upstream fixed end 12 and the downstream fixed end 13 and has at least one gentle curved portion 15. The reference axis 1 is a straight line connecting
6 is a single tube that makes a simple vibration on a circumferential line at a predetermined distance from each point of the reference shaft 16.

In this case, if the distance between the upstream fixed end 12 and the downstream fixed end 13 is L and the distance between the reference shaft 16 and the vibrating tube 11 is h, then approximately h ≦ 0.2.
It is desirable that the shape satisfy L.

The exciter 17 is provided at the center of the vibration tube 11. The vibration detection sensors 18 and 19 are provided on both sides of the vibration tube 11, respectively.

3 is a sectional view taken along line bb of the vibration tube 11 of FIG. 1, FIG. 4 is a sectional view taken along line aa, cc of the vibration tube 11 of FIG. 1, and FIG. 1
FIG. 4 is a perspective view showing a state of vibration of FIG. 2 and 3, the vibrating tube 11 is in the vicinity of the position A in the non-excited state.

In the excited state, the center of the vibration tube 11 moves on a circumference separated from the reference axis 16 by a radius R (x). At the position of the cross section bb, the radius R (b)
At the position of the cross section aa or cc on the distant circumference, the circumference at a distance R (a) or R (c) from the reference axis 16 is A →
Vibrates as B → A → C → A → B → (repeat).

In FIG. 5, A, B, and C correspond to the respective positions of the vibration tube 11 in FIGS. In addition, 12, 1
3 indicates a fixed end, and 16 indicates a reference axis.

As for the vibration detection and signal processing, the same processing as that of a normal Coriolis mass flow meter may be performed. For example, the vibration detection sensors 18 and 19 detect the Y component of the vibration, determine the phase difference between the two sensor outputs,
The mass flow rate flowing inside the tube can be obtained by adding temperature correction and the like.

Since the vibration tube 11 vibrates only within a circumferential surface equidistant from the reference shaft 16, the vibration tube 1
No matter where the position 1 is, the length of the vibration tube 11 does not change.

Therefore, the pulling force in the axial direction is always constant. That is, due to the change in the axial force,
Vibration leakage can be eliminated. By increasing the vibration isolation, the vibration inside the flowmeter becomes stable, and a highly accurate and stable Coriolis mass flowmeter can be realized.

More specifically, since the Q value of the internal vibration is increased, the influence of vibration noise is reduced, the power consumption is reduced, and the zero point and the span change due to the change in the amount of vibration leakage can be reduced. A mass flow meter is obtained. By increasing the vibration isolation in this way, the following advantages are exhibited.

As a result, (1) the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if external noise is applied, and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained. Can be

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected, and the zero point and span fluctuate. In the present invention, since the vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

Further, (4) measurement fluid FL _o flow path from the inlet flow meter (inlet) to the outlet (outlets), branched, or no gaps, since a single penetrating structure, the flow rate of loss less ,
A Coriolis mass flowmeter that is hard to clog and easy to clean is obtained.

(5) Not a straight tube but a vibrating tube 1
1 is previously bent 15 into a predetermined shape in a non-excited state, so that it is easy to absorb a change in ambient temperature at the bent portion 15 and a Coriolis mass flowmeter having good temperature characteristics can be obtained.

A Coriolis mass flowmeter that is not a general curved tube nor a perfect straight tube, but has a moderate curve, thereby realizing the advantages of a curved tube and a straight tube simultaneously.

FIG. 6 is an explanatory view of a main part of another embodiment of the present invention. Plate-shaped vibrating body 21,
Reference numeral 22 is perpendicular to the reference shaft 16 or the vibration tube 11, in this case, perpendicular to the reference shaft 16, one end is fixed to the vibration tube 11, and the other end is connected to the reference shaft 16 with the vibration tube 11. It is located on the opposite side. However, in this case, two are arranged at positions symmetrical to the center line 14.

As shown in FIG. 6, the vibration system has a shape symmetrical with respect to the X-axis direction. That is, the vibration tube 11, the vibration detection sensors 18, 19, and the vibrators 21, 22 are located at symmetrical positions with respect to a center line 14 (a reference axis of line symmetry) between the upstream fixed end 12 and the downstream fixed end 13. Exists.

At this time, the mass distribution and the shape of the vibrators 21 and 22 are adjusted, and the whole vibration system (vibration tube 11, vibration detection sensors 18 and 19, exciter 17, vibrator 21,
The center of gravity of 22) is arranged on the reference axis 16.

That is, when the shapes and weights of the vibration tube 11, the vibration detection sensors 18 and 19, and the exciter 17 are determined, the total mass M and the position of the center of gravity (Z: Z coordinate of the position of the center of gravity) are obtained.

The masses and shapes of the vibrators 21 and 22 are adjusted,
Assuming the total mass m and the center of gravity position z, the center of gravity of the entire vibration system is arranged on the reference axis 16 when the relationship of M × Z = m × z holds.

As a result, the center of gravity of the entire vibration system is
Since it is on the upper side, even when vibration noise is added from the outside or a shock is received, an abnormal operation such as an abnormal vibration of a portion distant from the center of gravity is unlikely to occur.

In addition, even when the vibration tube 11 is affected, it is symmetrical to the whole vibration system, and the influence tends to be relatively uniform. Even if the vibration is not normal, the vibration at the two points upstream and downstream of the vibration tube 11 is detected. This makes it possible to cancel noise.

As a result, a stable and accurate Coriolis mass flowmeter which is hardly affected by external vibration or impact can be obtained.

FIGS. 7, 8, 9 and 10 are explanatory diagrams of the main parts of another embodiment of the present invention. FIG. 9 is a diagram illustrating the vibration operation according to claim 3, showing a modal analysis result of a finite element method using a beam element.

7 is a perspective view, FIG. 8 is a projection view from the X direction in FIG. 7, FIG. 9 is a projection view from the Y direction in FIG. 7, and FIG. 10 is a projection view from the Z direction in FIG. A shape D in an initial state;
Both shapes E at maximum deformation are shown.

The vibrating tube 11 and the vibrating bodies 21 and 22
As shown by the arrow F in FIGS. 7, 8, 9, and 10, the initial deformation position D is deformed to the maximum positive deformation position E, and the original position D is returned again. The maximum negative deformation E is symmetric with respect to the plane, and returns to the initial position D.

The vibration system repeats such a simple vibration.
Note that this analysis is a linear analysis when the amount of deformation is small, and the actual amount of deformation is enlarged in FIGS. 7, 8, 9 and 10 for easy understanding.

In the third aspect, the mass distribution, shape and rigidity of the vibration tube 11 and the mass distribution, shape, rigidity and spacing of the vibrating bodies 21 and 22 are adjusted to adjust the entire vibration system (the vibration tube 11 and , Vibration detection sensors 18 and 19, and exciter 1
7 and the position of the center of gravity of the vibrators 21 and 22)
(See FIG. 8). The basic configuration explanatory diagram is the same as FIG.

At the position of the vibration node G, the vibration system generates a rotation component about the X axis, but the position does not move (X, Y,
Z coordinate does not change). When the shape of the vibration tube 11 is determined in advance, the center of gravity of the entire vibration system can be arranged on the node G of the vibration by adjusting the weight of the vibration bodies 21 and 22.

Note that the position of the vibration node G is
22 greatly depends on the mounting position. Generally, according to the center (or if it is centralized into one center), FIG.
As shown in FIG. 1, FIG. 12, FIG. 13, and FIG.
Positive direction of axis.

Note that FIG. 11, FIG. 12, FIG. 13, and FIG.
Shows the modal analysis result of the finite element method using the beam element.

FIG. 11 is a perspective view, FIG. 12 is a projection view from the X direction in FIG. 11, FIG. 13 is a projection view from the Y direction in FIG.
FIG. 14 is a projection view from the Z direction in FIG. 11, and shows both the shape D in the initial state and the shape E at the time of maximum deformation.

As shown in FIG. 15, FIG. 16, FIG. 17, and FIG.
Can be arranged. In addition, FIG. 15, FIG.
FIGS. 17 and 18 show modal analysis results of the finite element method using the beam element.

FIG. 15 is a perspective view, FIG. 16 is a projection view from the X direction in FIG. 15, FIG. 17 is a projection view from the Y direction in FIG.
FIG. 18 is a projection view from the Z direction in FIG. 15, and shows both the shape D in the initial state and the shape E in the maximum deformation.

This is because the vibrating tube 11 and the vibrating body 21
In addition to the large Y coordinate of the connection point 22, the vibrating tube 11 has a large deformation angle around the reference axis 16 near the center, and the vibrators 21 and 22 connected thereto also have a large angle. It is considered that the intersection between the bodies 21 and 22 and the Y axis is in the plus direction of the Y axis.

For the reasons described above, in order to set the center of gravity on the reference axis 16 and on the node G of vibration, it is sufficient to provide one vibrating body at the center to satisfy the purpose. Can not. Two vibrators 21 and 22 symmetrical in the upstream and downstream directions are required.

As a result, since the center of gravity of the entire vibration system does not move, useless vibration is eliminated and vibration isolation is further enhanced. By increasing the vibration isolation in this way, the following advantages can be obtained.

(1) The internal vibration system can realize a high Q value, and even if external noise is applied, the influence thereof is relatively small and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the amount of the dissipated energy is lost in the upstream and downstream of the vibrating tube 11, the internal vibration system is affected, and the zero point and the span fluctuate. Resulting in.

In the present invention, since the vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

(4) Even if a noise or impact in the translation direction, which is normally received from the outside, is added and the center of gravity performs a translational motion, it is a motion different from a normal excitation vibration. Can be easily distinguished.

A stable and highly accurate Coriolis mass flowmeter which is hardly affected by external vibrations and shocks can be obtained.

FIGS. 19, 20, 21 and 22 are views for explaining the operation of the main part of another embodiment of the present invention. The results of modal analysis of the finite element method using shell elements are shown. Note that the basic configuration explanatory diagram is the same as FIG.

FIG. 19 is a perspective view, FIG. 20 is a projection view from the X direction in FIG. 19, FIG. 21 is a projection view from the Y direction in FIG.
FIG. 22 is a projection view from the Z direction in FIG. 19, and shows both the shape D in the initial state and the shape E at the time of maximum deformation.

The vibrating tube 11 and the vibrating bodies 21 and 22
As shown by the arrow F in the figure, the simple vibration is repeated around the initial position D until the positive and negative maximum deformation positions. FIG.
9, FIG. 20, FIG. 21, and FIG. 22, the deformation amount is shown in an enlarged manner for easy viewing.

The mass distribution, shape and rigidity of the vibrating tube 11 and the mass distribution, shape, rigidity and spacing of the vibrating bodies 21 and 22 are adjusted to fix both end fixing portions 12 and 13 of the vibrating tube 11 in a steady excitation state. Is a torsion component ROTX around the reference axis 16 only, so that components FY and FZ orthogonal to the reference axis 16 due to the excitation force by the exciter 17 are not generated.

FIGS. 23 and 24 show calculation models that realize the fourth aspect. FIG. 23 is a front view from the Z direction, and FIG.
Is a perspective view. When stainless steel is used and the dimensions are as shown in FIGS. 23 and 24, the sum of the Z-direction forces applied to the fixing portions 12 and 13 at both ends is:

M = 32 g, ΣFZ ≒ 0.4 kgf M = 33 g, ΣFZ ≒ 0.13 kgf M = 33.5 g, ΣFZ ≒ 0 kgf At this time, the force applied to the fixed ends 12 and 13 is substantially eliminated.

As a result, in the steady excitation state, the force F of the translational component other than the torsional component ROTX around the reference axis 16 is applied to the fixed portions 12 and 13 at both ends of the vibrating tube 11.
Since Y and FZ do not occur, vibration hardly leaks outside.

The Coriolis mass flow having a much larger torsional rigidity (torsional rigidity = GIp = Gπd4 / 32 rigidity is effective as the fourth power of diameter) than the vibrating tube 11 with respect to the rotational force about the reference axis 16. Due to the presence of the housing 6 of the meter, it is possible to suppress it firmly.

By increasing the vibration isolation in this way, the following advantages can be obtained. (1) Since the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if external noise is applied, and the vibration is stable, a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the amount of the dissipated energy is disrupted between the upstream and downstream of the vibrating tube 11, the internal vibration system is affected, and the zero point and span fluctuate. Resulting in. In the present invention, since the vibration is always trapped inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

FIG. 25 is an explanatory view of a main part of another embodiment of the present invention. Vibration detection sensor 1
8 and 19 are provided at the other ends of the vibrators 21 and 22.

The vibration detecting sensors 18 and 19 are connected to the reference shaft 16.
Vibrating body 2 in the opposite direction to vibrating tube 11
By installing them near the ends of 1 and 22, vibration can be detected at an optimum position.

By locating at the tips of the vibrators 21 and 22, vibration can be measured at the place where the amplitude is the largest in the vibration system. Also, the phase difference generated by the Coriolis force becomes very large.

Actually, as a result of comparing the embodiment of FIG. 6 with the embodiment of FIG. 25 (corresponding to claim 6) by experiment, the following results are obtained as an example. The ratio of sensor amplitude / drive amplitude is shown in FIG.
In the embodiment, it is 0.8, and in the embodiment of FIG. 25, it is 3.5. Generated phase difference
<m rad> is 8.8 in the embodiment of FIG. 6 and 37.5 in the embodiment of FIG. Becomes

As described above, in both the amplitude ratio and the generated phase difference, values that are slightly more than four times as large as those in the embodiment of FIG. 6 were observed.

As a result, (1) If the measured amplitude is large, the S / N is improved. Conversely, if the measurement amplitude is the same as the conventional one, the excitation force can be reduced, and a Coriolis mass flowmeter with low power consumption can be obtained. If the maximum amplitude is small, the vibration energy is small, the leakage to the outside is small, the vibration isolation is easy, and a highly accurate and stable Coriolis mass flowmeter can be obtained.

(2) If the generated phase difference is large, the signal processing of the signal conversion part becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

Conversely, if the signal processing performance is equivalent to the conventional one, stable measurement can be performed up to the low flow rate region where the generated phase difference is small. A possible Coriolis mass flow meter is obtained.

After all, since the amplitude and the phase difference are four times or more larger, it is very advantageous and a dramatic improvement effect can be obtained.

FIGS. 26, 27, 28 and 29 are explanatory views of the operation of the main part of another embodiment of the present invention. FIG. 2
Excitation is performed in a higher-order vibration mode than the next mode. FIG. 25 shows the result of performing modal analysis on the embodiment in FIG. 25 by the finite element method using shell elements.

FIG. 26 is a perspective view, FIG. 27 is a projection view from the X direction in FIG. 26, FIG. 28 is a projection view from the Y direction in FIG.
FIG. 29 is a projection view from the Z direction in FIG. 26, and shows both the shape D in the initial state and the shape E in the maximum deformation.

In the third mode resonance state of the embodiment shown in FIG. 25, the resonance frequency is 267 Hz. Normally, when self-excited, the lowest vibration mode is easily excited, but in this embodiment,
The exciter 17 is adjusted so that the third-order mode is excited, and self-excited.

In the embodiment of FIG. 25, the primary mode resonance frequency is 153 Hz, and the vibration mode shapes are as shown in FIGS. 30, 31, 32, and 33.

FIG. 30 is a perspective view, FIG. 31 is a projection view from the X direction in FIG. 30, FIG. 32 is a projection view from the Y direction in FIG.
FIG. 33 is a projection view from the Z direction in FIG. 30, and shows both the shape D in the initial state and the shape E in the maximum deformation.

In FIGS. 30, 31, 32 and 33,
The entire vibration system is deformed in the + Z direction. Since it is not a circumferential vibration, the excitation force is directly applied to the ends 12 and 13,
Large forces in the X direction and the Z direction are applied to the ends 12 and 13.

The second mode resonance frequency in the embodiment of FIG. 25 is 250 Hz, and has the vibration mode shapes as shown in FIGS. 34, 35, 36 and 37.

FIG. 34 is a perspective view, FIG. 35 is a projection view from the X direction in FIG. 34, FIG. 36 is a projection view from the Y direction in FIG.
FIG. 37 is a projection view from the Z direction in FIG. 34, and shows both the shape D in the initial state and the shape E at the time of maximum deformation.

Referring to FIGS. 34, 35, 36, and 37,
In the vicinity of the center of the vibration tube 11, the deformation in the Z direction is plus or minus reversed. Since the amount of deformation of the vibration tube 11 itself is small, the generation of Coriolis force is also small,
Not a very practical vibration mode.

In the embodiment shown in FIG. 25, the fourth-order mode resonance frequency is 397 Hz, which is a vibration mode shape as shown in FIGS. 38, 39, 40 and 41.

38 is a perspective view, FIG. 39 is a projection view from the X direction in FIG. 38, FIG. 40 is a projection view from the Y direction in FIG.
FIG. 41 is a projection view from the Z direction in FIG. 38, and shows both the shape D in the initial state and the shape E in the maximum deformation.

In FIG. 38, FIG. 39, FIG. 40 and FIG. 41, although the shapes are complicated deformations, since the resonance frequency is high,
It does not have much adverse effect.

As a result, the following advantages can be obtained by exciting in the second, third, or higher order mode. (1) It is easy to set the excitation frequency higher. Vibration at low frequency is susceptible to vibration noise in the field, whereas high frequency excitation provides a Coriolis mass flowmeter that is less susceptible to vibration noise.

(2) The resonance frequencies of the excitation mode and the vibration mode generated by the Coriolis force can be made close to each other. In the embodiment of FIG. 25, the drive frequency is 260 Hz, and the Coriolis approximation mode is close to 246 Hz.

From the following equation, since P = 1.057 and Q = 1000, the dynamic magnification G = 8.5 is large and the generated phase difference is large. Here, dynamic magnification G = (1−P ² ) / ((1−P ² ) ² + (P / Q)) P = (drive frequency) / (resonance frequency of Coriolis approximation mode)

(3) If the generated phase difference is large, the signal processing of the signal conversion unit becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

On the other hand, if the signal processing performance is equivalent to the conventional one, it is possible to measure stably up to a low flow rate region where the generated phase difference is small, or to measure the mass flow rate of the gas originally generated with a small phase difference. A possible Coriolis mass flow meter is obtained.

FIG. 42, FIG. 43 and FIG. 44 are explanatory diagrams of the main parts of another embodiment of the present invention. 42 is a front view, FIG. 43 is a plan view of FIG. 42, and FIG.
42 is a side view of FIG. 42.

The compensator 31 is provided inside the housing 61. In the compensator 31, the vibration tube 11
, An exciter 17 and vibration detection sensors 18 and 19 are provided.

In this case, an example is shown in which coils 171, 181, 191 and magnets 172, 182, 192 are used for the exciter 17 and the vibration detection sensors 18, 19. The compensator 31 is provided in parallel with the reference axis 9,
It is long in the parallel direction, and both ends are fixedly supported at both ends of the vibration tube 11.

In the above configuration, as shown in FIG.
When the exciter 17 is operating, the power of F ₁ and F _2, the coil 171 and the magnet 172 is repelled. With that power,
The vibrating tube 11 and the vibrating bodies 21 and 22 rotate clockwise in FIG. 44 around the vicinity of the reference axis like T _{1 and} T ₃ .

On the other hand, the compensator 31 generates T ₂ , T ₄
As shown in the figure, the vibration tube 11 and the vibrators 21 and 22 rotate counterclockwise.

Since the vibration tube 11 and the compensator 31 are connected to each other, the fixed ends 12 and 13, which are the connecting portions thereof,
The right-handed force and the left-handed force cancel each other, which has the effect of reducing such components around the axis. Outside the compensator 31,
The rotation component about the reference axis 16 can be prevented from leaking.

As a result, since the compensator 31 is installed in the housing 6, the vibration tube 11, the vibrators 21,
2. Forces act on the vibration detection sensors 18 and 19 and the compensator 31 in mutually opposite directions via the exciter 17,
A counter-rotational vibration occurs around the center.

At the fixed ends 12 and 13 where the vibration tube 11 and the compensator 31 are connected, forces act in opposite directions and cancel each other to form a node of vibration. Since not only the translational component but also the rotational component about the reference axis 16 can be suppressed, the vibration insulation can be further enhanced.

By increasing the vibration isolation as described above, the following advantages are exhibited. (1) Since the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if external noise is applied, and the vibration is stable, a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with small energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected, and the zero point and span fluctuate. In the present invention, since the vibration is always trapped inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

(4) Even if a stress is applied from the outside, the internal vibration can be kept stable by supporting it with the compensator 31. That is, a stable high vibration is hardly affected by piping stress and thermal stress. An accurate Coriolis mass flowmeter can be obtained.

FIG. 45 is an explanatory view of a main part of another embodiment of the present invention. In the present embodiment, the flexible structure 41 that absorbs expansion and contraction in the direction of the reference shaft 16 and rotational vibration around the reference shaft 16 is provided between the upstream fixed end 12, the downstream fixed end 13, and the compensator 31. Of the vibration tube 11.

As a result, since the flexible structure portion 41 is provided in the vibration tube 11 between the upstream fixed end 12, the downstream fixed end 13, and the compensator 31, (1) thermal expansion is absorbed. This makes it possible to obtain a Coriolis mass flowmeter capable of performing stable and accurate measurement over a wide temperature range.

(2) Even when pipe stress is applied, the flexible structure 41 can absorb the stress and does not affect the inside, so that a stable and accurate Coriolis mass flowmeter can be obtained.

[0116]

As described above, according to the first aspect of the present invention,
According to (1), the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if added, and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with small energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disturbed, the internal vibration system is affected, and the zero point and span fluctuate. In the present invention, since the vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

(4) The measurement fluid channel is provided at the inlet (inlet) of the flow meter.
There is no branch or gap from the outlet to the outlet
Because of the single penetrating structure, a Coriolis mass flowmeter with low flow velocity loss, less clogging, and easy cleaning can be obtained.

(5) Since the vibrating tube is not completely straight but is curved into a predetermined shape in a non-excited state, the curved portion can easily absorb changes in ambient temperature, and the temperature characteristics , A good Coriolis mass flowmeter can be obtained.

A Coriolis mass flowmeter which is not a general curved tube nor a perfect straight tube, but has an appropriate curve, thereby realizing the advantages of a curved tube and a straight tube at the same time is obtained.

According to the second aspect of the present invention, since the center of gravity of the entire vibration system is on the reference axis, even if external vibration noise is applied or a shock is applied, a portion distant from the center of gravity will cause abnormal vibration. It is unlikely that an abnormal operation such as an abnormal operation will occur.

Further, even if the vibration is affected, it is symmetrical to the whole vibration system and the influence is likely to occur relatively uniformly. Even if the vibration is not normal, it is necessary to detect the vibrations at two points upstream and downstream of the vibration tube. Thus, it is possible to cancel the noise.

From these, a stable and accurate Coriolis mass flowmeter which is hardly affected by external vibration or impact can be obtained.

According to the third aspect of the present invention, since the center of gravity of the whole vibration system does not move, there is no useless vibration, and vibration isolation is further enhanced. By increasing the vibration isolation in this way, the following advantages can be obtained.

(1) The internal vibration system can realize a high Q value, and even if external noise is applied, its influence is relatively small and the vibration is stable, so that a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with a small amount of energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the amount of the dissipated energy is disrupted in the upstream and downstream of the vibrating tube, the internal vibration system is affected, and the zero point and span change. Would.

In the present invention, since vibration is always confined inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

(4) Even if a translational noise or impact is applied, which is normally received from the outside, and the center of gravity performs a translational motion, the motion is different from the normal excitation vibration. Can be easily distinguished.

A stable and highly accurate Coriolis mass flowmeter which is hardly affected by external vibrations and shocks can be obtained.

According to claim 4 of the present invention, (1) the internal vibration system can realize a high Q value, the influence of external noise is relatively small, and the vibration is stable. A strong Coriolis mass flow meter is obtained.

(2) Since stable excitation can be realized with small energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the amount of dissipated energy is disrupted upstream and downstream of the vibrating tube, the internal vibration system is affected, and the zero point and span fluctuate. Would. In the present invention, since the vibration is always trapped inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

According to the fifth aspect of the present invention, (1) S / N is improved if the measured amplitude is large. Conversely, if the measurement amplitude is the same as the conventional one, the excitation force can be reduced, and a Coriolis mass flowmeter with low power consumption can be obtained. If the maximum amplitude is small, the vibration energy is small, the leakage to the outside is small, the vibration isolation is easy, and a highly accurate and stable Coriolis mass flowmeter can be obtained.

(2) If the generated phase difference is large, the signal processing in the signal conversion portion becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

Conversely, if the signal processing performance is equivalent to the conventional one, stable measurement can be performed up to the low flow rate region where the generated phase difference is small, or the mass flow rate measurement of gas originally having a small generated phase difference can be performed. A possible Coriolis mass flow meter is obtained.

As a result, since both the amplitude and the phase difference are large, a very advantageous and dramatic improvement effect can be obtained.

According to the sixth aspect of the present invention, the following advantages are obtained by exciting in the second, third or higher order mode. (1) It is easy to set the excitation frequency higher. Vibration at low frequency is susceptible to vibration noise in the field, whereas high frequency excitation provides a Coriolis mass flowmeter that is less susceptible to vibration noise.

(2) The resonance frequency between the excitation mode and the vibration mode generated by the Coriolis force can be made close to each other, and the generated phase difference is large.

(3) If the generated phase difference is large, the signal processing of the signal conversion unit becomes easy. That is, a Coriolis mass flowmeter capable of realizing stable and highly accurate performance even with a simple and inexpensive signal processing circuit can be obtained.

Conversely, if the signal processing performance is equivalent to the conventional one, it is possible to measure stably up to the low flow rate region where the generated phase difference is small, or to measure the mass flow rate of the gas originally generated with a small phase difference. A possible Coriolis mass flow meter is obtained.

According to the seventh aspect of the present invention, since the compensator is provided in the housing, the vibrating tube, the vibrator, the vibration detecting sensor and the compensator are forced in opposite directions via the exciter. Works to generate reverse rotation vibration about the reference axis.

At the fixed end where the vibration tube and the compensator are connected, forces act in opposite directions and cancel each other to form a node of vibration. Since not only the translational component but also the rotational component about the reference axis can be suppressed, the vibration insulation can be further enhanced.

By increasing the vibration isolation as described above, the following advantages are exhibited. (1) Since the internal vibration system can realize a high Q value, the influence of external noise is relatively small even if external noise is applied, and the vibration is stable, a Coriolis mass flowmeter resistant to external vibration noise can be obtained.

(2) Since stable excitation can be realized with small energy, a Coriolis mass flowmeter with low current consumption can be obtained.

(3) If the amount of vibration energy dissipated to the outside changes, or if the balance of the amount dissipated upstream and downstream is disrupted, the internal vibration system is affected, and the zero point and span fluctuate. In the present invention, since the vibration is always trapped inside, there is no need to worry about this, and a highly accurate Coriolis mass flowmeter can be obtained.

(4) Even if stress is applied from the outside, the internal vibration can be kept stable by supporting it with the compensator. That is, stable and high precision is hardly affected by piping stress and thermal stress. A Coriolis mass flowmeter is obtained.

According to claim 8 of the present invention, the flexible structure portion is
Since it is provided in the vibration tube between the upstream fixed end, the downstream fixed end, and the compensator, (1) it is possible to absorb thermal expansion, and it is stable with high accuracy over a wide temperature range. A Coriolis mass flowmeter capable of measurement is obtained.

(2) Even when a pipe stress is applied, it can be absorbed by the flexible structure and does not affect the inside, and a stable and accurate Coriolis mass flowmeter can be obtained.

Therefore, according to the present invention, a Coriolis mass flowmeter with improved stability, accuracy and vibration resistance can be realized by improving the insulation of internal vibration.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a main part configuration of an embodiment of the present invention.

FIG. 2 is a side view of FIG.

FIG. 3 is an operation explanatory diagram of FIG. 1;

FIG. 4 is an operation explanatory diagram of FIG. 1;

FIG. 5 is an operation explanatory diagram of FIG. 1;

FIG. 6 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 7 is an explanatory perspective view of a main part configuration of another embodiment of the present invention.

FIG. 8 is a projection view from the X direction in FIG. 7;

FIG. 9 is a projection view from the Y direction in FIG. 7;

FIG. 10 is a projection view from the Z direction in FIG. 7;

FIG. 11 is a perspective view for explaining the operation of FIG. 7;

FIG. 12 is a projection view from the X direction in FIG. 11;

FIG. 13 is a projection view from the Y direction in FIG. 11;

FIG. 14 is a projection view from the Z direction in FIG. 11;

FIG. 15 is a perspective view illustrating the operation of FIG. 7;

FIG. 16 is a projection view from the X direction in FIG. 15;

17 is a projection view from the Y direction in FIG.

18 is a projection view from the Z direction in FIG.

FIG. 19 is a perspective view for explaining an operation of a main part of another embodiment of the present invention.

FIG. 20 is a projection view from the X direction in FIG. 19;

FIG. 21 is a projection view from the Y direction in FIG. 19;

FIG. 22 is a projection view from the Z direction in FIG. 19;

23 is an operation explanatory view of FIG. 19 and is a front view from the Z direction.

FIG. 24 is an operation perspective explanatory view of FIG. 19;

FIG. 25 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 26 is an explanatory perspective view of an operation of a main part of another embodiment of the present invention.

FIG. 27 is a projection view from the X direction in FIG. 26;

FIG. 28 is a projection view from the Y direction in FIG. 26;

FIG. 29 is a projection view from the Z direction in FIG. 26;

FIG. 30 is an explanatory perspective view of an operation in a primary mode.

FIG. 31 is a projection view from the X direction in FIG. 30;

FIG. 32 is a projection view from the Y direction in FIG. 30.

FIG. 33 is a projection view from the Z direction in FIG. 30;

FIG. 34 is an explanatory perspective view of an operation in a secondary mode.

FIG. 35 is a projection view from the X direction in FIG. 34;

FIG. 36 is a projection view from the Y direction in FIG. 34;

FIG. 37 is a projection view from the Z direction in FIG. 34.

FIG. 38 is a perspective view showing the operation of the fourth mode.

FIG. 39 is a projection view from the X direction in FIG. 38;

40 is a projection view from the Y direction in FIG. 38.

FIG. 41 is a projection view from the Z direction in FIG. 38;

FIG. 42 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 43 is a plan view of FIG. 42.

FIG. 44 is a side view of FIG. 42.

FIG. 45 is an explanatory diagram of a main part configuration of another embodiment of the present invention.

FIG. 46 is an explanatory diagram of a configuration of a conventional example generally used in the related art.

FIG. 47 is an explanatory view of the configuration of another conventional example generally used in the prior art.

FIG. 48 is an explanatory diagram of the operation in FIG. 46.

FIG. 49 is an explanatory diagram of the operation in FIG. 47.

50 is an explanatory diagram of the operation in FIG. 47.

[Explanation of symbols]

 2 Flange 6 Housing 11 Vibration tube 12 Upstream fixed end 13 Downstream fixed end 14 Middle line 15 Gentle curved portion 16 Reference axis 17 Exciter 171 Coil 172 Magnet 18 Vibration detection sensor 181 Coil 182 Magnet 19 Vibration detection sensor 191 Coil 192 Magnet 21 Vibrator 22 Vibrator 31 Compensator 41 Flexible structure

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[Procedure amendment]

[Submission date] June 29, 1998

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] FIG.

[Correction method] Change

[Correction contents]

FIG. 44

Claims (8)

[Claims] 1. A Coriolis mass flowmeter for deforming and vibrating a vibrating tube by a flow of a measuring fluid in a vibrating tube and a Coriolis force generated by the flow of the measuring fluid and angular vibration of the vibrating tube. A straight line connecting the upstream fixed end and the downstream fixed end, which is symmetrical with respect to a middle line equidistant from the downstream fixed end and has at least one gentle curved portion, is used as a reference axis. A Coriolis mass flowmeter comprising a single vibrating tube that makes a simple vibration on a circumferential line at a predetermined distance from each point. A plate-shaped vibrating body perpendicular to said reference axis or said vibrating tube, one end of which is fixed to said vibrating tube and the other end of which is disposed on the opposite side of said vibrating tube with respect to said reference axis. The mass distribution and shape of the vibrating tube and the mass distribution and shape of the vibrating body are adjusted so that the center of gravity of the entire vibration system is arranged on the reference axis.
The Coriolis mass flowmeter described. 3. An axis perpendicular to said reference axis or said vibrating tube, one end of which is fixed to said vibrating tube, and the other end of which is arranged on the opposite side of said vibrating tube with respect to said reference axis and at a position symmetrical to said midline. At least two plate-shaped vibrators are provided, and the center of gravity of the entire vibration system is excited by adjusting the mass distribution, shape, and rigidity of the vibrating tube, and the mass distribution, shape, rigidity, and spacing of the vibrator. 3. The Coriolis mass flowmeter according to claim 1, wherein the Coriolis mass flowmeter is arranged at a position of a vibration node of the vibration. 4. An end which is orthogonal to said reference axis or said vibrating tube, one end of which is fixed to said vibrating tube, and the other end of which is disposed on the opposite side of said vibrating tube with respect to said reference axis and is symmetrical with respect to said center line. At least two plate-shaped vibrators are provided, and the mass distribution, shape, and rigidity of the vibrating tube, and the mass distribution, shape, rigidity, and spacing of the vibrator are adjusted to make the vibration in a steady excitation state. The force generated at both ends fixed portions of the tube is made only a torsional component around the reference axis, so that a component orthogonal to the reference axis caused by the excitation force by the exciter is prevented from being generated. The Coriolis mass flowmeter according to any one of claims 1 to 3. 5. A plate-shaped vibrating body orthogonal to said reference axis or said vibrating tube, one end of which is fixed to said vibrating tube, and the other end of which is disposed on the opposite side of said vibrating tube with respect to said reference axis. The Coriolis mass flowmeter according to any one of claims 1 to 4, further comprising a vibration detection sensor provided at the other end of the vibrating body. 6. The Coriolis mass flowmeter according to claim 1, further comprising an exciter for exciting the vibrating tube in a higher order vibration mode than a second order mode. 7. A compensator provided in parallel with the reference axis and having both ends fixedly supported at both ends of the vibrating tube, an exciter and a detector provided between the compensator and the vibrating tube. The Coriolis mass flowmeter according to any one of claims 1 to 6, further comprising: 8. A flexible structure provided on the vibrating tube between the upstream fixed end, the downstream fixed end, and the compensator for absorbing expansion and contraction in the direction of the reference axis and rotational vibration around the reference axis. The Coriolis mass flowmeter according to claim 7, further comprising a part.